Filter unit



FIG. 1 is a front elevational view of a filter unit showing my new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a light side view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is a perspective views thereof;

In the drawings, the dot/dash broken lines immediately adjacent to the outer edges of the filter unit shown in FIG. 6; represent boundaries of the claim. ALL other broken lines shown in the drawings depict portions of the filter unit that form no part of the claimed design. 

CLAIM The ornamental design for a filter unit, as shown and described. 